Today there are many ways to pay for services and articles. At some machines, paying can be done either with coins, paper money, or with a charge card. Common for most of these types of vending machines are that service staff regularly are either emptying the machine of coins, or filling it with tickets or receipt paper or other types of articles that are provided in the machine, such as e.g., snacks or drinks. The service staff can either get access to the machine by a key or by some type of electronic identification.
One problem with providing access by a key is that if the key goes astray all concerned locks have to be replaced, which of course results in large expenses. If, on the other hand, access is given by electronic identification, there is a dependency on a power supply to get access to the machine.
In the patent specification U.S. Pat. No. 5,402,475, a parking machine is described that automatically communicates with the service staff to tell them when something is wrong with the machine. Every machine in the system can also communicates with a central coordination unit, wherein some functions in the machine may be controlled from a remote location.
In the published patent application US 2006/0032418, a lock for an electric safe is described. The lock consists of both an electronic unit and a mechanical unit that makes it possible to open the electric safe even if the electronic system fails.